MODIFICATION OF THE SURFACE OF A POWER COLLECTOR BEFORE COATING WITH MOLTENED METAL

Abstract

A method for manufacturing an anode electrode for a battery cell comprises providing a current collector and forming a layer on the current collector to create a coated current collector. The layer comprises a metal or metal oxide that is immiscible with molten lithium. The method includes immersing the coated current collector in molten lithium to coat the current collector.

Description

INTRODUCTION

[0001] The information contained in this section is intended to provide a general context for the disclosure. Work by the presently named inventors, to the extent described in this introduction, as well as aspects of the description that may not otherwise be considered prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against this disclosure.

[0002] The present disclosure relates to current collectors for battery cell electrodes and, more particularly, to a method for coating battery cell current collectors with metal or metal oxide prior to immersion in molten lithium metal.

[0003] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, comprise one or more electric machines and a battery system with one or more battery cells, modules, and / or packs. A battery control module is used to control the charging and discharging of the battery system during charging and / or driving. Electric vehicle manufacturers are striving for higher power density to increase the range of their vehicles. SUMMARY

[0004] A method of manufacturing an anode electrode for a secondary battery cell comprises providing a current collector and forming a layer on the current collector to create a coated current collector. The layer comprises one of a metal or a metal oxide that is immiscible with molten lithium. The method comprises immersing the coated current collector in molten lithium to coat the coated current collector.

[0005] In other embodiments, the current collector comprises a braided current collector. The current collector is made of a material selected from a group consisting of copper (Cu), stainless steel (SS), nickel (Ni), and alloys thereof. The current collector includes a plurality of first wires and a plurality of second wires overlapping and arranged at an angle relative to the plurality of first wires. The plurality of first wires and the plurality of second wires have a thickness in the range of 4 µm to 100 µm. The current collector includes 100 to 300 openings per square inch between the plurality of first wires and the plurality of second wires. One of the metal and the metal oxide is selected from a group consisting of zinc (Zn), nickel (Ni), bismuth (Bi), tin (Sn), and germanium (Ge).One of the metal and the metal oxide is selected from a group consisting of zinc oxide (Zn oxide), nickel oxide (Ni oxide), bismuth oxide (Bi oxide), tin oxide (Sn oxide) and germanium oxide (Ge oxide).

[0006] For other features, the layer is deposited electrochemically on the current collector. The layer is deposited on the current collector in a vacuum. The layer is sputtered onto the current collector. The layer is deposited on the current collector with a laser. The layer has a thickness in the range of 5 nm to 200 nm.

[0007] A method of manufacturing an anode electrode comprises providing a braided current collector made of a material selected from a group consisting of copper, stainless steel, and nickel, and forming a layer on the braided current collector to create a coated braided current collector. The layer comprises one of a metal and a metal oxide selected from a group consisting of nickel (Ni), zinc (Zn), bismuth (Bi), tin (Sn), germanium (Ge), and oxides thereof, and has a thickness in the range of 5 nm to 200 nm. The method comprises immersing the coated braided current collector in molten lithium to coat the coated braided current collector.

[0008] In other features, the braided current collector comprises a plurality of first wires and a plurality of second wires arranged at an angle relative to the plurality of first wires. The plurality of first wires and the plurality of second wires have a thickness in the range of 4 µm to 100 µm. The braided current collector includes 100 to 300 openings per square inch between the plurality of first wires and the plurality of second wires.

[0009] In other features, one of the layers is electrochemically deposited on the mesh current collector, the layer is vacuum deposited on the mesh current collector, the layer is sputtered onto the mesh current collector, and the layer is laser deposited on the mesh current collector.

[0010] An anode electrode for a storage battery cell comprises a braided current collector made of a material selected from a group consisting of copper, stainless steel, and nickel. A layer is disposed on the braided current collector. The layer comprises one of a metal and a metal oxide selected from a group consisting of nickel (Ni), zinc (Zn), bismuth (Bi), tin (Sn), germanium (Ge), and oxides thereof, and has a thickness in the range of 5 nm to 200 nm. A lithium layer formed from molten lithium coats the layer.

[0011] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are for illustrative purposes only and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present disclosure will be more fully understood from the detailed description and the accompanying drawings, in which: Fig. 1 shows an example of a battery cell with anode electrodes, cathode electrodes and separators according to the present disclosure in a cross-sectional view, Fig. 2A and Fig. 2B illustrate an example of a copper current collector after immersion in molten lithium, each in a plan view, Fig. 2C shows an example of a coated copper current collector after immersion in molten lithium according to the present disclosure in a plan view, Fig. 3 shows an example of a diagram of the binary phases for lithium and copper, Fig. 4A and Fig. 4B illustrates an example of intergranular attack when immersing a copper current collector in molten lithium, Fig. 5 and Fig. 6 shows an example of the grain boundaries of copper being dissolved in molten lithium when using the uncoated current collector, each in an enlarged view, Fig. 7A illustrates an example of electrochemically coating the current collector with a metal or metal oxide layer that is not miscible with molten lithium, according to the present disclosure, Fig. 7B illustrates an example of immersing the coated mesh current collector in molten lithium to form a lithium anode electrode according to the present disclosure, Fig. 8 shows an example of a method for manufacturing coated mesh current collectors that are immersed in molten lithium to form a lithium anode electrode of a battery cell according to the present disclosure, and Fig. 9 illustrates an example of a coated mesh current collector after immersion in molten lithium in accordance with the present disclosure.

[0013] Reference symbols may be reused in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0014] Although the battery cells and / or electrodes according to the present disclosure are described herein in the context of electric vehicles, the battery cells and / or electrodes may be used in stationary applications and / or in other types of applications.

[0015] Battery cells comprise anode electrodes, cathode electrodes, and separators arranged in a predetermined sequence within a housing. The anode electrodes comprise an anode active layer arranged on one or both sides of an anode current collector. The cathode electrodes comprise a cathode active layer arranged on one or both sides of a cathode current collector.

[0016] In some examples, the anode and cathode current collectors comprise wire mesh, foil, or expanded metal. For example, mesh current collectors comprise overlapping wires arranged at an angle and made of copper, stainless steel, nickel, and alloys thereof. The wire mesh current collector may be made of wires with a thickness of 4 µm to 100 µm (e.g., 30 µm). In some examples, the wire mesh current collector has approximately 100 to 300 openings per square inch (e.g., 100).

[0017] The present disclosure relates to methods for coating the current collector (e.g., a copper braid current collector) with molten lithium metal (e.g., lithium or lithium alloy). For example, when copper-based braid current collectors are immersed in molten lithium, a portion of the copper in the copper braid current collector dissolves due to a dissolution-assisted (intergranular) corrosion reaction between the molten lithium and the copper in the molten lithium. Dissolution causes portions of the wires of the braid current collector to dissolve. Furthermore, the dissolved copper contaminates the molten lithium bath, adversely affecting the density of lithium anode electrodes fabricated using the contaminated molten lithium bath.

[0018] Before immersing the current collector in the molten lithium bath, it is coated with a metal or metal oxide that is immiscible with molten lithium. The metal or metal oxide layer can, for example, comprise a material selected from a group consisting of tin (Sn), zinc (Zn), nickel (Ni), bismuth (Bi), germanium (Ge), and their oxides. The metal or metal oxide layer prevents intergranular attack on the base metal of the current collector (e.g., copper).

[0019] With reference to Fig. 1, a storage battery cell 10 comprises cathode electrodes 20-1, 20-2, ..., and 20-C, where C is an integer greater than one. The cathode electrodes 20 comprise a layer 24 made of cathode-active material, which is arranged on one or both sides of the cathode current collectors 26. The storage battery cell 10 comprises the anode electrodes 40-1, 40-2, ..., and 40-A, where A is an integer greater than one. The anode electrodes 40 comprise a layer 42 made of anode-active material, which is arranged on one or both sides of the anode current collectors 46. The cathode electrodes 20, the anode electrodes 40, and the separators 32 are arranged in a predetermined order in a housing 50. For example, separators 32 are arranged between the cathode electrodes 20 and the anode electrodes 40.

[0020] With reference now to Fig. Figures 2A to 2C show an example of the dissolution of the base metal of the current collector upon immersion in lithium metal. In this example, the current collector comprises a copper current collector 80 with a wire mesh. Fig. 2A and Fig. 2B, the copper current collector 80 is uncoated before immersion in the molten lithium. As in Fig. As can be seen in Figure 2B, at 84 there is limited lithium wetting of the copper current collector 80, and the copper of the copper wire mesh dissolves due to a dissolution-assisted (intergranular) corrosion reaction between the molten lithium and the copper in the molten lithium.

[0021] In Fig. 2C, a current collector 90 comprises a copper wire mesh comprising an outer layer 91 disposed on the current collector. The outer layer 91 comprises a metal or metal oxide species that is immiscible with molten lithium. Miscibility is the property of two substances to mix and form a homogeneous mixture.

[0022] The outer layer 91 may, for example, comprise a material selected from a group consisting of tin (Sn), zinc (Zn), nickel (Ni), bismuth (Bi), germanium (Ge), and their oxides. The outer layer 91 may be applied by any suitable method, e.g., by electrochemical deposition, vacuum deposition, sputtering, laser deposition, or other methods. When the current collector 90 with the outer layer 91 is immersed in molten lithium 92, the molten lithium 92 does not dissolve the base metal of the current collector. The molten lithium 92 can penetrate into the gaps between the wires of the current collector 90 and improve the wetting of the current collector 90.

[0023] With reference to Fig. Figure 3 shows a diagram illustrating the binary phases of lithium and copper. A liquid lithium phase is shown at 210, a liquid and solid copper phase at 220, a solid lithium and copper phase at 230, and a solid copper phase at 240. The diagram of the binary Li-Cu phases shows that the mutual solubility of Li and Cu is limited (close to zero). It should be noted that there are no intermetallic phases in the Li-Cu system. When liquid Li comes into contact with the Cu, a two-phase equilibrium is established, and some of the Cu is replaced by a Li-rich liquid. Since liquid Li does not undergo an intermetallic reaction with Cu, the Li-rich liquid has direct access to the grain boundaries in the Cu substrate, providing a pathway for intergranular attack. Liquid tin (Sn), on the other hand, behaves differently, as it would dissolve Cu and form intermetallic phases between the two elements.

[0024] With reference now to Fig. 4A and Fig. 4B shows a dissolution-assisted (intergranular) corrosion reaction. In Fig. 4A, copper 310 (e.g. the base metal of the current collector in some examples) encompasses grain boundaries 314 and 322. In Fig. 4B, intergranular attack occurs when copper 310 is immersed in molten lithium 320. The molten lithium 320 penetrates the grain boundary 322 and eventually causes partial dissolution of the copper 310.

[0025] With reference now to Fig. 5 and Fig. 6, molten lithium enters the grain boundaries and dissolves some of the copper. The molten lithium-copper alloy solidifies at the grain boundary, weakening the grain boundary. Some of the Cu grains exhibit weakened intergranular bonds and separate from the rest of the Cu substrate (e.g., the copper mesh), leading to decrepitation of the Cu. The copper dissolved in the molten Li precipitates during solidification, resulting in lithium contamination. Fig. 5 and Fig. 6 show the precipitation of copper into the molten lithium.

[0026] To prevent the base metal (e.g., Cu) of the current collector from dissolving when immersed in molten lithium, the current collector is coated with an outer layer of metal or metal oxide. The metal or metal oxide species is immiscible with molten lithium. The layer can include, for example, tin (Sn), zinc (Zn), nickel (Ni), bismuth (Bi), germanium (Ge), and their oxides.

[0027] The outer layer may be applied to the current collector (prior to immersion in the molten lithium) using any suitable method (e.g., electrochemical deposition, vacuum deposition, sputtering, laser deposition, or other deposition methods). In some examples, the metal or metal oxide layer is deposited on the current collector by electron beam evaporation and / or thermal vacuum evaporation. In some examples, the metal or metal oxide layer is deposited on the current collector by chemical vapor deposition (CVD) and / or physical vapor deposition (PVD). In some examples, the metal or metal oxide layer is deposited on the current collector by atomic layer deposition (ALD), molecular beam epitaxy (MBE), and / or arc evaporation. In some examples, the metal or metal oxide layer is deposited by sputtering methods (e.g.,DC and RF sputtering, DC magnetron sputtering, and / or reactive sputtering). In some examples, the metal and / or metal oxide layer is deposited on the current collector by laser deposition techniques such as pulsed laser deposition.

[0028] With reference now to Fig. 7A and Fig. Figure 7B shows an example of the fabrication of the current collector by electrochemical deposition. First, the metal or metal oxide layer is electrodeposited on the current collector in one bath. The current collector, along with the metal or metal oxide layer, is then immersed in molten lithium in another bath.

[0029] In Fig. 7A, a current collector 520 (e.g., a copper braid current collector) is connected to a negative terminal of a power supply 522 and immersed in a bath 510 comprising a molten metal salt or a molten metal oxide 514. The bath 510 (or the molten metal salt or molten metal oxide 514) is connected to the positive terminal of the power supply 522. The power supply 522 creates a voltage difference that causes the metal or metal oxide to electroplate onto an outer surface of the current collector 520, forming a layer. When the layer has reached a sufficient thickness (typically proportional to the plating time), the current collector 520 is removed from the bath 510 (and includes the metal or metal oxide layer). In some examples, the metal or metal oxide layer has a thickness in the range of 5 nm to 200 nm, although other thicknesses may be used.In some examples, the current collector is coated for a period of time ranging from 15 seconds to 2 minutes, although other coating times may be used.

[0030] In Fig. 7B, the current collector 520 with the metal or metal oxide layer is immersed in a bath 530 containing molten lithium 534 after the layer has been deposited. The molten lithium 534 coats the current collector 520 without dissolving the base metal (e.g., Cu) of the current collector 520.

[0031] In Fig. 8 shows a method 600 for fabricating a coated mesh current collector, a lithium anode electrode, and / or a secondary battery cell. At 610, a current collector is provided. At 614, a metal or metal oxide layer is deposited on the current collector 614 by any suitable method (e.g., electrochemical deposition or other methods). Once the layer is applied to the current collector, the current collector is immersed in molten lithium at 620 to create a lithium anode electrode. At 624, the lithium-coated anode is placed in the secondary battery cell stack.

[0032] In Fig.Figure 9 shows a metal or metal oxide layer 650 on an outer surface of a base metal of a current collector 640 (e.g., a copper mesh current collector). The metal or metal oxide layer 650 acts as a barrier to a molten lithium layer 660 and prevents intergranular attack at grain boundaries 642 and 644. By introducing a metal / metal oxide layer between the lithium and the copper, dissolution at the grain boundaries of the copper current collector is avoided. This allows the energy density of the lithium anodes to be affected by the copper.

[0033] The above description is merely illustrative and is not intended to limit the disclosure, its application, or uses in any way. The broad teachings of the disclosure may be embodied in a variety of forms. Therefore, while this disclosure includes specific examples, the true scope of the disclosure should not be limited thereto, since other changes will become apparent after studying the drawings, the patent specification, and the following claims. It is understood that one or more steps within a method may be performed in different orders (or simultaneously) without altering the principles of the present disclosure.Furthermore, although the embodiments are each described above as having specific features, each or more of these features described with respect to one embodiment of the disclosure may be implemented and / or combined with features of any of the other embodiments, even if this combination is not expressly described. In other words, the described embodiments are not mutually exclusive, and an exchange of one or more embodiments for one another remains within the scope of this disclosure.

[0034] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaging," "coupled," "adjacent," "beside," "on top of," "above," "below," and "disposed." If a relationship between first and second elements is not explicitly described as "direct" in the above disclosure, that relationship may be a direct relationship, with no other intervening elements between the first and second elements, or an indirect relationship, with one or more intervening elements (either spatial or functional) between the first and second elements.As used herein, the term "A, B and / or C" should be construed as logical (A ORed with B ORed with C) using a non-exclusive logical OR, and not as "at least one of A, at least one of B and at least one of C".

[0035] In the figures, the direction of an arrow, as indicated by the arrowhead, generally illustrates the flow of information (e.g., data or instructions) of interest to the illustration. For example, if element A and element B exchange a lot of information, but the information passed from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is passed from element B to element A. Furthermore, for information being sent from element A to element B, element B may send requests for or acknowledgments of receipt of the information to element A.

Claims

[1] A method for producing an anode electrode for a storage battery cell, comprising: Providing a current collector, Forming a layer on the current collector to produce a coated current collector, wherein the layer comprises a metal or a metal oxide that is immiscible with molten lithium, and Immersing the coated current collector in molten lithium to coat the coated current collector. [2] The method of claim 1, wherein the current collector comprises a braided current collector. [3] The method of claim 1, wherein the current collector is made of a material selected from a group consisting of copper (Cu), stainless steel (SS), nickel (Ni) and alloys thereof. [4] The method of claim 2, wherein the current collector comprises a plurality of first wires and a plurality of second wires overlapping and arranged at an angle relative to the plurality of first wires. [5] The method of claim 4, wherein the plurality of first wires and the plurality of second wires have a thickness in the range of 4 µm to 100 µm. [6] The method of claim 4, wherein the braided current collector comprises 100 to 300 openings per square inch between the plurality of first wires and the plurality of second wires. [7] The method of claim 1, wherein one of the metal and the metal oxide is selected from a group consisting of zinc (Zn), nickel (Ni), bismuth (Bi), tin (Sn) and germanium (Ge). [8] The method according to claim 1, wherein one of the metal and the metal oxide is selected from a group consisting of zinc oxide (Zn oxide), nickel oxide (Ni oxide), bismuth oxide (Bi oxide), tin oxide (Sn oxide) and germanium oxide (Ge oxide). [9] The method of claim 1, wherein the layer is electrochemically deposited on the current collector. [10] The method of claim 1, wherein the layer is vacuum deposited on the current collector.

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